The conventional OLED (Organic Light Emitting Diode) technology has many special characters, including self emitting, simple structure, ultrathin, wide viewing angles, low power consumption as well as flexible displays and more. In many aspects, including picture quality, response speed, power consumption, thickness and viewing angles, it is better than traditional LCDs (Liquid Crystal Display) and LEDs (Light-Emitting Diode). Also, OLED's display mode is different to that of a traditional LCD, since OLED is adopting very thin layers of organic materials and glass plates, no backlight, color filter, or liquid crystal needed, as long as any electric currents are passing through, the organic materials (that is, the organic thin layer) will emit light. Thus, in recently years, OLED research spreads into a hot topic among all leading global displayer manufacturers in a fast speed. Following the maturation of OLED technologies, displayers with OLED screens (such as TV sets, monitors, projectors and more.) will gradually substitute those with traditional LCD screens and LED screens. However, a power supply module with a stable performance and high efficiency is the key factor for OLED displayers to work stably thus reflects their practical values.
Taking an intelligent TV set for example. In prior arts, in power supply designs for intelligent TV sets, each of the different screen sizes and different power consumptions for the whole set requires different power supply architectures. Usually, such a power supply needs to output both a +12V voltage and a +24V voltage. In a traditional power board, the transformation and output of both +12V voltage and +24V voltage are sharing the same voltage transformer. For example, as shown in FIG. 1, two different windings in the same transformer are outputting a +12V voltage and a +24V voltage, respectively. In FIG. 2, the same winding of a transformer outputs a +24V voltage while also outputs a +12V voltage from its center. When an ON/OFF signal arrives from outside, turning on (or off) the device, the Pulse-Width Modulation (PWM) circuit will be controlled to start to work, then the rectified DC current (that is, the current for input, as shown in FIGS. 1 and 2) will be transformed into +12V and +24V voltages for output, by a transformer. However, when the output power is large, due to sharing the same transformer, the two different output voltages, +12V voltage and +24V voltage, could affect each other, and make the power output unstable thus cause unpredictable results, which extends the period of R&D as well as debug processes. Also, the design of sharing the same transformer increases the burden of adjusting the circuit, while also increases the loss in the power board, thus it decreases the output efficiency. In extreme cases, this could even affect the working stability of the whole device and reduce the service life. Also, sharing one transformer requires a stricter process design. Since the work principle of OLED is that, an organic thin film is driven by a current then emits light, thus its response speed is much faster than that of a LED, and any changes of picture colors on screen will result in fast changes in electric current, so, if sharing one transformer, the fast changing current could affect the output of +12V voltage, then unpredictable results could appear, which eliminates the stability of the system, and brings difficulties to the processes of R&D and debug, thus extends the study period; Also, tiny current fluctuations could eliminate the picture quality and even the service life of an OLED displayer. Thus, stricter requirements on power output, especially on the stability of the electric current are required.
In addition, a displayer based on OLED technology owns a faster response speed comparing to other display methods. In a traditional power source architecture, both +12V voltage and +24V voltage have the same timing sequences, when the power is on or off, shown as FIG. 3. When a switch signal ON/OFF is sent to the power board, both +12V voltage and +24V voltage transforms will be turned on or off at the same time. As shown in FIG. 3, at the time point T1, the curves of +12V voltage, +24V voltage and a switch signal ON/OFF will rise at the same time (i.e., turned on); at time point T2, the curves of +12V voltage, +24V voltage and the power switch signal ON/OFF will decline at the same time (i.e., turned off). In these cases, the effects of fast response character of OLED could cause some unpredictable failures including blurred screens and more, thus a traditional power supply design is hard to fulfill the requirements of an OLED screen.